[Trisquel-users] how to install and set session of MATE, LXDE, XFCE?

[sora]

This maybe a dumb question but I have just used trisquel, I am a mainly a  
debian user, since trisquel is based on ubuntu which is based on debian. I  
cannot find any tutorial on how to change the GNOME and set the session to  
MATE or ther desk env like XFCE or LXDE. I have installed the mate-desktop  
but I don't know how to change session to use the MATE instead of GNOME  
environment. And is it also possible to install lxde, xfce alongside with  
mate? I had a problem in fedora in which you cannot install all of them  
without interfering with another.